Am 15.06.2012 19:48, schrieb clipka:
> Am 15.06.2012 17:14, schrieb Warp:
>> Le_Forgeron<jgr### [at] freefr> wrote:
>>> If the sky is "blue", why do you see a yellow sun ?
>>
>> The sun is not yellow. It's white.
>
> That depends on the color space.
>
> In sRGB (whitepoint = D65 = ~6500K), the sun is a pale yellow.
>
> In Wide Gamut RGB (Whitepoint = D50 = ~5000K), the sun is actually a
> pale blue.
>
> If you use a color space with the equal-energy point (E) as whitepoint,
> the sun is even a pale green.
>

This makes actually not much sense as all RGB-color-spaces are device 
dependent. So when you use e.g. WideGamut RGB or Adobe RGB as a 
*viewing* color space with a sRGB device you are obviously doing 
something very wrong.


> That's both for the sun's /actual/ color (without atmospheric effects,
> i.e. as seen from space) of ~5900K, as well as the sun's apparent color
> on earth at daytime of ~5500K.

Close ;)

See attachment, the output from test_sun.pov (a POV-Ray scene file I've 
written for lightsys IV - at www.ignorancia.org) that compares the 
actual spectral data with the blackbody radiation. I think there is also 
an espd*.inc file for the sun filtered by earth atmosphere, for people 
who want to play around with it.

I've just noticed (quite surprised) that the file is from April 2003, 
doesn't time fly by...

-Ive

Post a reply to this message

Attachments:
Download 'test_sun.png' (176 KB)

Preview of image 'test_sun.png'